/* pdu.h -- CoAP message structure
 *
 * Copyright (C) 2010--2012 Olaf Bergmann <bergmann@tzi.org>
 *
 * This file is part of the CoAP library libcoap. Please see
 * README for terms of use. 
 */

#ifndef _PDU_H_
#define _PDU_H_

#include "config.h"
#include "coap_list.h"
#include "uri.h"

#ifdef WITH_LWIP
#include <lwip/pbuf.h>
#endif

/* pre-defined constants that reflect defaults for CoAP */

#define COAP_DEFAULT_RESPONSE_TIMEOUT  2 /* response timeout in seconds */
#define COAP_DEFAULT_MAX_RETRANSMIT    4 /* max number of retransmissions */
#define COAP_DEFAULT_PORT           5683 /* CoAP default UDP port */
#define COAP_DEFAULT_MAX_AGE          60 /* default maximum object lifetime in seconds */
#ifndef COAP_MAX_PDU_SIZE
#define COAP_MAX_PDU_SIZE           1400 /* maximum size of a CoAP PDU */
#endif /* COAP_MAX_PDU_SIZE */

#define COAP_DEFAULT_VERSION           1 /* version of CoAP supported */
#define COAP_DEFAULT_SCHEME        "coap" /* the default scheme for CoAP URIs */

/** well-known resources URI */
#define COAP_DEFAULT_URI_WELLKNOWN ".well-known/core"

#ifdef __COAP_DEFAULT_HASH
/* pre-calculated hash key for the default well-known URI */
#define COAP_DEFAULT_WKC_HASHKEY   "\345\130\144\245"
#endif

/* CoAP message types */

#define COAP_MESSAGE_CON               0 /* confirmable message (requires ACK/RST) */
#define COAP_MESSAGE_NON               1 /* non-confirmable message (one-shot message) */
#define COAP_MESSAGE_ACK               2 /* used to acknowledge confirmable messages */
#define COAP_MESSAGE_RST               3 /* indicates error in received messages */

/* CoAP request methods */

#define COAP_REQUEST_GET       1
#define COAP_REQUEST_POST      2
#define COAP_REQUEST_PUT       3
#define COAP_REQUEST_DELETE    4

/* CoAP option types (be sure to update check_critical when adding options */

#define COAP_OPTION_IF_MATCH      1 /* C, opaque, 0-8 B, (none) */
#define COAP_OPTION_URI_HOST      3 /* C, String, 1-255 B, destination address */
#define COAP_OPTION_ETAG          4 /* E, opaque, 1-8 B, (none) */
#define COAP_OPTION_IF_NONE_MATCH 5 /* empty, 0 B, (none) */
#define COAP_OPTION_URI_PORT      7 /* C, uint, 0-2 B, destination port */
#define COAP_OPTION_LOCATION_PATH 8 /* E, String, 0-255 B, - */
#define COAP_OPTION_URI_PATH     11 /* C, String, 0-255 B, (none) */
#define COAP_OPTION_CONTENT_FORMAT 12 /* E, uint, 0-2 B, (none) */
#define COAP_OPTION_CONTENT_TYPE COAP_OPTION_CONTENT_FORMAT
#define COAP_OPTION_MAXAGE       14 /* E, uint, 0--4 B, 60 Seconds */
#define COAP_OPTION_URI_QUERY    15 /* C, String, 1-255 B, (none) */
#define COAP_OPTION_ACCEPT       17 /* C, uint,   0-2 B, (none) */
#define COAP_OPTION_LOCATION_QUERY 20 /* E, String,   0-255 B, (none) */
#define COAP_OPTION_PROXY_URI    35 /* C, String, 1-1034 B, (none) */
#define COAP_OPTION_PROXY_SCHEME 39 /* C, String, 1-255 B, (none) */
#define COAP_OPTION_SIZE1        60 /* E, uint, 0-4 B, (none) */

/* option types from draft-ietf-coap-observe-09 */

#define COAP_OPTION_OBSERVE       6 /* E, empty/uint, 0 B/0-3 B, (none) */
#define COAP_OPTION_SUBSCRIPTION  COAP_OPTION_OBSERVE

/* selected option types from draft-core-block-04 */

#define COAP_OPTION_BLOCK2       23 /* C, uint, 0--3 B, (none) */
#define COAP_OPTION_BLOCK1       27 /* C, uint, 0--3 B, (none) */

#define COAP_MAX_OPT             63 /**< the highest option number we know */

/* CoAP result codes (HTTP-Code / 100 * 40 + HTTP-Code % 100) */

/* As of draft-ietf-core-coap-04, response codes are encoded to base
 * 32, i.e.  the three upper bits determine the response class while
 * the remaining five fine-grained information specific to that class.
 */
#define COAP_RESPONSE_CODE(N) (((N)/100 << 5) | (N)%100)

/* Determines the class of response code C */
#define COAP_RESPONSE_CLASS(C) (((C) >> 5) & 0xFF)

#ifndef SHORT_ERROR_RESPONSE
/** 
 * Returns a human-readable response phrase for the specified CoAP
 * response @p code. This function returns @c NULL if not found.
 * 
 * @param code The response code for which the literal phrase should
 * be retrieved.
 * 
 * @return A zero-terminated string describing the error, or @c NULL
 * if not found.
 */
char *coap_response_phrase(unsigned char code);

#define COAP_ERROR_PHRASE_LENGTH 32 /**< maximum length of error phrase */

#else
#define coap_response_phrase(x) ((char *)NULL)

#define COAP_ERROR_PHRASE_LENGTH 0 /**< maximum length of error phrase */
#endif /* SHORT_ERROR_RESPONSE */

/* The following definitions exist for backwards compatibility */
#if 0 /* this does not exist any more */
#define COAP_RESPONSE_100      40 /* 100 Continue */
#endif
#define COAP_RESPONSE_200      COAP_RESPONSE_CODE(200)  /* 2.00 OK */
#define COAP_RESPONSE_201      COAP_RESPONSE_CODE(201)  /* 2.01 Created */
#define COAP_RESPONSE_304      COAP_RESPONSE_CODE(203)  /* 2.03 Valid */
#define COAP_RESPONSE_400      COAP_RESPONSE_CODE(400)  /* 4.00 Bad Request */
#define COAP_RESPONSE_404      COAP_RESPONSE_CODE(404)  /* 4.04 Not Found */
#define COAP_RESPONSE_405      COAP_RESPONSE_CODE(405)  /* 4.05 Method Not Allowed */
#define COAP_RESPONSE_415      COAP_RESPONSE_CODE(415)  /* 4.15 Unsupported Media Type */
#define COAP_RESPONSE_500      COAP_RESPONSE_CODE(500)  /* 5.00 Internal Server Error */
#define COAP_RESPONSE_501      COAP_RESPONSE_CODE(501)  /* 5.01 Not Implemented */
#define COAP_RESPONSE_503      COAP_RESPONSE_CODE(503)  /* 5.03 Service Unavailable */
#define COAP_RESPONSE_504      COAP_RESPONSE_CODE(504)  /* 5.04 Gateway Timeout */
#if 0  /* these response codes do not have a valid code any more */
#  define COAP_RESPONSE_X_240    240   /* Token Option required by server */
#  define COAP_RESPONSE_X_241    241   /* Uri-Authority Option required by server */
#endif
#define COAP_RESPONSE_X_242    COAP_RESPONSE_CODE(402)  /* Critical Option not supported */

/* CoAP media type encoding */

#define COAP_MEDIATYPE_TEXT_PLAIN                     0 /* text/plain (UTF-8) */
#define COAP_MEDIATYPE_APPLICATION_LINK_FORMAT       40 /* application/link-format */
#define COAP_MEDIATYPE_APPLICATION_XML               41 /* application/xml */
#define COAP_MEDIATYPE_APPLICATION_OCTET_STREAM      42 /* application/octet-stream */
#define COAP_MEDIATYPE_APPLICATION_RDF_XML           43 /* application/rdf+xml */
#define COAP_MEDIATYPE_APPLICATION_EXI               47 /* application/exi  */
#define COAP_MEDIATYPE_APPLICATION_JSON              50 /* application/json  */

/* Note that identifiers for registered media types are in the range 0-65535. We
 * use an unallocated type here and hope for the best. */
#define COAP_MEDIATYPE_ANY                         0xff /* any media type */

/* CoAP transaction id */
/*typedef unsigned short coap_tid_t; */
typedef int coap_tid_t;
#define COAP_INVALID_TID -1

#ifdef WORDS_BIGENDIAN
typedef struct {
  unsigned int version:2;	/* protocol version */
  unsigned int type:2;		/* type flag */
  unsigned int token_length:4;	/* length of Token */
  unsigned int code:8;	        /* request method (value 1--10) or response code (value 40-255) */
  unsigned short id;		/* message id */
  unsigned char token[];	/* the actual token, if any */
} coap_hdr_t;
#else
typedef struct {
  unsigned int token_length:4;	/* length of Token */
  unsigned int type:2;		/* type flag */
  unsigned int version:2;	/* protocol version */
  unsigned int code:8;	        /* request method (value 1--10) or response code (value 40-255) */
  unsigned short id;		/* transaction id (network byte order!) */
  unsigned char token[];	/* the actual token, if any */
} coap_hdr_t;
#endif

#define COAP_MESSAGE_IS_EMPTY(MSG)    ((MSG)->code == 0)
#define COAP_MESSAGE_IS_REQUEST(MSG)  (!COAP_MESSAGE_IS_EMPTY(MSG)	\
				       && ((MSG)->code < 32))
#define COAP_MESSAGE_IS_RESPONSE(MSG) ((MSG)->code >= 64)

#define COAP_OPT_LONG 0x0F	/* OC == 0b1111 indicates that the option list in a
				 * CoAP message is limited by 0b11110000 marker */

#define COAP_OPT_END 0xF0	/* end marker */

#define COAP_PAYLOAD_START 0xFF	/* payload marker */

/**
 * Structures for more convenient handling of options. (To be used with ordered
 * coap_list_t.) The option's data will be added to the end of the coap_option
 * structure (see macro COAP_OPTION_DATA).
 */
typedef struct {
  unsigned short key;		/* the option key (no delta coding) */
  unsigned int length;
} coap_option;

#define COAP_OPTION_KEY(option) (option).key
#define COAP_OPTION_LENGTH(option) (option).length
#define COAP_OPTION_DATA(option) ((unsigned char *)&(option) + sizeof(coap_option))

/** Header structure for CoAP PDUs */

typedef struct {
  size_t max_size;	/**< allocated storage for options and data */

  coap_hdr_t *hdr;
  unsigned short max_delta;	/**< highest option number */
  unsigned short length;	/**< PDU length (including header, options, data)  */
  unsigned char *data;		/**< payload */

#ifdef WITH_LWIP
  struct pbuf *pbuf; /**< lwIP PBUF. The allocated coap_pdu_t will always reside inside the pbuf's payload, but the pointer has to be kept because no exact offset can be given. This field must not be accessed from outside, because the pbuf's reference count is checked to be 1 when the pbuf is assigned to the pdu, and the pbuf stays exclusive to this pdu. */
#endif

} coap_pdu_t;

/** Options in coap_pdu_t are accessed with the macro COAP_OPTION. */
#define COAP_OPTION(node) ((coap_option *)(node)->options)

#ifdef WITH_LWIP
/**
 * Creates a CoAP PDU from an lwIP @p pbuf, whose reference is passed on to
 * this function.
 *
 * The pbuf is checked for being contiguous, for having enough head space for
 * the PDU struct (which is located directly in front of the data, overwriting
 * the old other headers), and for having only one reference. The reference is
 * stored in the PDU and will be freed when the PDU is freed.
 *
 * (For now, these are errors; in future, a new pbuf might be allocated, the
 * data copied and the passed pbuf freed).
 *
 * This behaves like coap_pdu_init(0, 0, 0, pbuf->tot_len), and afterwards
 * copying the contents of the pbuf to the pdu.
 *
 * @return A pointer to the new PDU object or @c NULL on error.
 */
coap_pdu_t * coap_pdu_from_pbuf(struct pbuf *pbuf);
#endif

/** 
 * Creates a new CoAP PDU of given @p size (must be large enough to hold the 
 * basic CoAP message header (coap_hdr_t). The function returns a pointer to
 * the node coap_pdu_t object on success, or @c NULL on error. The storage
 * allocated for the result must be released with coap_delete_pdu().
 * 
 * @param type The type of the PDU (one of COAP_MESSAGE_CON,
 *             COAP_MESSAGE_NON, COAP_MESSAGE_ACK, COAP_MESSAGE_RST). 
 * @param code The message code.
 * @param id   The message id to set or COAP_INVALID_TID if unknown.
 * @param size The number of bytes to allocate for the actual message.
 * 
 * @return A pointer to the new PDU object or @c NULL on error.
 */
coap_pdu_t *
coap_pdu_init(unsigned char type, unsigned char code, 
	      unsigned short id, size_t size);

/** 
 * Clears any contents from @p pdu and resets @c version field, @c
 * length and @c data pointers. @c max_size is set to @p size, any
 * other field is set to @c 0. Note that @p pdu must be a valid
 * pointer to a coap_pdu_t object created e.g. by coap_pdu_init().
 */
void coap_pdu_clear(coap_pdu_t *pdu, size_t size);

/**
 * Creates a new CoAP PDU. The object is created on the heap and must be released
 * using coap_delete_pdu();
 * 
 * @deprecated This function allocates the maximum storage for each
 * PDU. Use coap_pdu_init() instead. 
 */
coap_pdu_t *coap_new_pdu();

void coap_delete_pdu(coap_pdu_t *);

/**
 * Parses @p data into the CoAP PDU structure given in @p result. This
 * function returns @c 0 on error or a number greater than zero on
 * success.
 *
 * @param data   The raw data to parse as CoAP PDU
 * @param length The actual size of @p data
 * @param result The PDU structure to fill. Note that the structure must
 *               provide space for at least @p length bytes to hold the
 *               entire CoAP PDU.
 * @return A value greater than zero on success or @c 0 on error.
 */
int coap_pdu_parse(unsigned char *data, size_t length, coap_pdu_t *result);

/**
 * Adds token of length @p len to @p pdu. Adding the token destroys
 * any following contents of the pdu. Hence options and data must be
 * added after coap_add_token() has been called. In @p pdu, length is
 * set to @p len + @c 4, and max_delta is set to @c 0.  This funtion
 * returns @c 0 on error or a value greater than zero on success.
 *
 * @param pdu  The PDU where the token is to be added.
 * @param len  The length of the new token.
 * @param data The token to add.
 * @return A value greater than zero on success, or @c 0 on error.
 */
int coap_add_token(coap_pdu_t *pdu, size_t len, const unsigned char *data);

/**
 * Adds option of given type to pdu that is passed as first
 * parameter. coap_add_option() destroys the PDU's data, so
 * coap_add_data() must be called after all options have been added.
 * As coap_add_token() destroys the options following the token,
 * the token must be added before coap_add_option() is called.
 * This function returns the number of bytes written or @c 0 on error.
 */
size_t coap_add_option(coap_pdu_t *pdu, unsigned short type, 
		       unsigned int len, const unsigned char *data);

/**
 * Adds option of given type to pdu that is passed as first
 * parameter, but does not write a value. It works like coap_add_option with
 * respect to calling sequence (i.e. after token and before data).
 * This function returns a memory address to which the option data has to be
 * written before the PDU can be sent, or @c NULL on error.
 */
unsigned char *coap_add_option_later(coap_pdu_t *pdu, unsigned short type,
		      unsigned int len);

/**
 * Adds given data to the pdu that is passed as first parameter. Note
 * that the PDU's data is destroyed by coap_add_option(). coap_add_data()
 * must be called only once per PDU, otherwise the result is undefined.
 */
int coap_add_data(coap_pdu_t *pdu, unsigned int len, const unsigned char *data);

/**
 * Retrieves the length and data pointer of specified PDU. Returns 0 on error
 * or 1 if *len and *data have correct values. Note that these values are
 * destroyed with the pdu.
 */
int coap_get_data(coap_pdu_t *pdu, size_t *len, unsigned char **data);

#endif /* _PDU_H_ */
